Japanese people less likely to evacuate during future tsunamis

Disasters are supposed to teach people valuable lessons. But new
research shows that following the Tohoku earthquake and subsequent tsunami on 11 March,
2011, Japanese residents have become less likely to evacuate during
a dangerous event.

The magnitude 9.0 Tohoku earthquake and tsunami -- the largest
in Japanese history -- were responsible for more than 15,000 deaths
and an estimated $210 billion (£134 billion) in property
damage.

After the 2010 Chilean earthquake, almost exactly one year
before the Tohoku disaster, Oki asked Japanese residents a set of
questions related to tsunami preparedness. At the time, roughly 70
percent correctly identified that a 10-foot tsunami is a hazard and
60 percent said they would evacuate in the event of one that tall.
Even 1.5 feet of swiftly moving water can carry a person off and
drown them, and waves only 6.5 feet high can wash away or destroy
wooden houses.

But when the same questions were asked again one month after the
Tohoku disaster, the numbers had nearly halved. Only 45 percent of
respondents knew that a 10-foot tsunami was hazardous and only 31
percent said they would evacuate if they heard a warning that one
was coming. People mostly misidentified a 16-foot tsunami as the
point at which to evacuate. Such public perception could become
dangerous in the case of future earthquakes and tsunamis.

Oki speculated that the reason for the strange result has to do
with a psychological effect called the anchoring heuristic. "Laypersons are highly
inclined to make a judgment based on previous information given to
them," she said.

The effect holds even if the information is unrelated. The size
of the number seems to be the important factor. For example, if
people are first told that 1,100 people die every year from
electrocution, and then asked to estimate the total causalities
from floods they will provide a lower answer than people who are
first told that 10,000 people are killed in car accidents each
year. The higher number becomes an "anchor point," prompting higher
estimates.

With a month of Japanese headlines over and over exclaiming at
the record-breaking 130-foot tsunami, the public's approximations
of dangerous tsunami heights inched upward. The solution, Oki said,
is to include proper information alongside the enormous tsunami
figures. News reports could save future lives if they added one
phrase: a 6.5-foot tsunami could wash away your house.